The above-described laser light source module is composed of a semiconductor laser array obtained by arranging a plurality of semiconductor laser elements in a direction orthogonal to a light axis of a laser beam, a sub-mount substrate made of an insulating material and on which a power feeding circuit pattern is formed, a heat sink made of a material having high thermal conductivity such as copper, and a stem on which a plurality of power feeding lead pins are side-by-side arranged in a standing manner. Meanwhile, the semiconductor laser array is mounted on the sub-mount substrate, the sub-mount substrate is mounted on the heat sink, and the heat sink is mounted on the stem. Then, by electrically bonding the lead pin and the sub-mount substrate, and the sub-mount substrate and the array semiconductor laser element by a method such as wire bonding or solder bonding and applying current to the lead pin, the semiconductor laser array may be driven to output laser light.
Stress is loaded on the laser element when this is driven and temperature thereof increases, due to difference in linear expansion coefficient between the same and the sub-mount substrate on which this is mounted. In a case of an array semiconductor laser element, dimension of the element is larger than that of a single laser element, and the stress acting on each laser element also is relatively large. Also, since an oscillation wavelength is changed according to the temperature in the laser element and the reliability thereof lowers at high temperature, it is desirable that the temperature in the semiconductor laser array is made uniform as far as possible at an appropriate temperature.
For the reason described above, it is conventionally proposed to use the material such as copper tungsten (hereinafter, CuW) excellent in thermal conductivity and having the linear expansion coefficient similar to that of the semiconductor laser array as the material of a heat sink member on which the semiconductor laser array or the sub-mount substrate is mounted. For example, the Patent Documents 1 and 2 propose a structure in which a plate member made of CuW is interposed between the semiconductor laser array and a water-cooling device.
Also, the Patent Document 3 proposes a structure in which the sub-mount material is CuW and the plate member made of copper (hereinafter, Cu), which becomes an insulating substrate and a power feeding path, and the semiconductor laser array are mounted on the sub-mount, and an electrode and the power feeding path of the semiconductor laser array are electrically bonded by means of wire bonding. In the laser light source module having such a structure, the power consumption and an amount of heat generation of the power feeding path may be made small even when large current is applied by using the CuW sub-mount and the Cu plate member of which electric resistance is small as the power feeding path.
Patent Document 1: Specification of Japanese Patent No. 3816194
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2007-221109
Patent Document 3: Japanese Patent Application Laid-Open No. 2006-128236